1. Field of the Invention
The present invention relates to a termite sensor and a termite intrusion detecting system for detecting intrusion of termites into wooden buildings and the like.
2. Discussion of the Background
It is well known that wooden buildings and wooden structures suffer severe damage due to eating by termites.
According to their habit, when intruded into a wooden building or a wooden structure, they eat holes in its wood part to make their nests. Therefore, once the termites intruded into a wooden building or the like, its wooden part is damaged severely by their eating in a very short time. Wooden buildings and wooden structures are often collapsed due to eating by termites.
As one conventional method for avoiding such a situation, there is known a method in which an agent is coated on wooden part of a wooden building or a wooden structure to prevent termites from eating.
However, recent trend restricting toxicity tends to prohibit the use and sales of the agent of which effect lasts long, or of which effect and toxicity are strong.
On the contrary, the low persistent and low toxic agent which is outside the restriction requires to increase its coating frequency to attain enough effect, resulting in more time and more labor.
Now, under such a situation where the agent of strong effect should not be employed, it is effective to employ a termite sensor which can detect instantaneously the intrusion of termites together with a weak agent. Even after the effect of the agent decreases, measures can be taken before the wooden building or the wooden structure is eaten much.
Further, since the intrusion of termites can be detected when such a termite sensor is used, measures for exterminating the termites can be taken at the time when detected. Therefore, when termites not yet intruded, the agent of unnecessarily strong toxicity is not required to be employed. Therefore, the use of highly toxic agent is unnecessary and the amount of use of the agent can be reduced, resulting in much advantages from the view point of material and environment safety.
From such view points, various termite sensors have been provided.
One of them is a termite sensor utilizing infra-red light.
This termite sensor consists of an infra-red light emitting part and a probe for detecting infra-red light. It makes use of a principle that, when a termite goes through between the infra-red light emitting part and the detecting probe of infra-red light, the infra-red light is interrupted to make lower output of the detector. In addition, with this termite sensor, since the number of interruptions can be measured, the number of intruded termites can be grasped.
However, this termite sensor using infra-red light may recognize other insects than a termite such as a black ant, or small animals such as a mouse, as a termite.
Further, when dirt or the like is stuck between the infra-red light emitting part and the detecting probe of infra-red light, it may be also wrongly recognized as a termite to induce malfunction. Therefore, in order to prevent this from occurring, the infra-red light path between the infra-red light emitting part and the detecting probe of infra-red light is required to be cleaned periodically, resulting in more labor for maintenance of the termite sensor.
The other form of termite sensor than one using infra-red light is under research, in which a circuit is formed with conductive paint on wood part or the like which are liable to be eaten by termites. When a termite eats a part of wood, the conductive circuit is disconnected to be detected electrically. This type of termite sensor is simple in its structure and is also easy in maintaining.
However, in the sensor, if the circuit of conductive paint remains connected even when a part of wood has been damaged by the termite, thus not being destroyed, destruction continues without being detected of the intrusion of the termite.
Thus, the aforementioned existing termite sensor has problems in reliability of detection and maintenance.